Hindustani Classical Music is a North Indian classical music tradition that has been evolving from the 12th centuries AD onwards, in what is now northern India and Pakistan, and also Bangladesh, Nepal and Afghanistan. The tradition was born out of a cultural synthesis from several musical streams: the vedic chant tradition dating back to approx. one millennia BCE, the equally ancient Persian tradition of Musiqi-e assil, and also existent folk traditions prevalent in the region. The terms North Indian Classical Music or Shāstriya Sangeet are also occasionally used.
Around the 12th century, Hindustani classical music diverged from the principle which eventually came to be identified as Carnatic classical music. The central notions in both these systems are that of a melodic mode or raga, sung to a rhythmic cycle or tala. The tradition dates back to the ancient Samaveda, (lit. sāma=ritual chant), which deals with the norms for chanting of srutis or hymns such as the Rig Veda. These principles were refined in the Natyashastra by Bharata (2nd-3d c. CE) and the Dattilam (probably 3d-4th c. AD). In medieval times, many of the melodic systems were fused with ideas from Persian music, particularly through the influence of sufi composers like Amir Khusro, and later in the Moghul courts. Noted composers such as Tansen flourished, along with religious groups like the Vaishnavites. After the 16th century, the singing styles diversified into different gharanas patronized in different princely courts. Around 1900, Pandit Vishnu Narayan Bhatkhande consolidated the musical structures of Hindustani Classical music into a number of thaats. In the 20th century, Hindustani classical music has become popular across the world through the influence of artistes like Ravi Shankar, Ali Akbar Khan and many others.
Indian classical music has 7 basic notes (Sa Re Ga Ma Pa Dha Ni), with five interspersed half-notes, resulting in a 12-note scale. Unlike the 12-note scale in Western music, the base frequency of the scale is not fixed, and intertonal gaps (temper) may also vary; however with the gradual replacement of the sarangi by the harmonium, an equal tempered scale is increasingly used. The performance is set to a melodic pattern (raga or raag) characterized in part by specific ascent (Arohana) and descent (Avarohana) sequences, which may not be identical. Other characteristics include King (Vadi) and Queen (Samavadi) notes and a unique note phrase (Pakad). In addition each raga has its natural register (Ambit) and glissando (Meend) rules, as well as features specific to different styles and compositions within the raga structure. Performances are usually marked by considerable improvisation within these norms.